At 34, Frank Wang has turned his dream of flying robots into the world’s biggest drone company—and a $4.5 billion fortune. Now, as the market for his devices explodes, his old colleague is trying to take him down.

With ingenuity, capital and a little creative chemistry, billionaire C. Dean Metropoulos and Apollo Global’s Andy Jhawar rescued one of America’s most beloved snacks—and set themselves up to feast on a $2 billion gain.